This invention relates to ink supply systems for ink jet printheads.
In many ink jet printheads it is important to maintain a negative pressure at the orifices from which ink is ejected in order to avoid weeping of ink from the orifices when the printhead is not operating. In addition, it is occasionally necessary to purge the printhead by ejecting ink under pressure through the printhead. It is also necessary in many cases to refill the reservoir from which ink is supplied to the printhead from a remote ink supply periodically in order to maintain a desired level of ink in the ink reservoir and to provide a remote ink supply which can be quickly and easily connected to the printhead in an inexpensive manner.
Certain prior art arrangements such as those described in the Robinson U.S. Pat. No. 4,187,511, the Matsumoto U.S. Pat. No. 4,536,777, the Eremity et al. U.S. Pat. No. 4,602,662 and the Mizusawa et al. U.S. Pat. No. 4,677,448 provide a remote ink supply from which ink is drawn to a reservoir for an ink jet head by a vacuum arrangement but these arrangements are complex and expensive. In other prior art arrangements such as described, for example, in the Okamura et al. U.S. Pat. No. 5,485,187, the ink level in the reservoir from which ink is supplied to a printhead is maintained at a desired spacing below the orifices in the printhead so as to produce a desired negative pressure at the orifices in the ink jet head and positive pressure may be applied for purging but the level of ink in a remote ink supply must be the same as the level of ink in the reservoir. The prior art, moreover, does not disclose a simple and inexpensive dual reservoir ink supply system for an ink jet printhead in which the ink in the reservoir can maintained at a desired level while permitting convenient replenishment of the reservoir from a remote ink supply which may be disposed at any level and also providing for purging of the printhead in a convenient manner, nor does it provide a simple and convenient arrangement for connecting and removing a remote ink supply.